<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    var findTheDifference = function (s, t) {
      // 取巧方法， 改变了原数据
      for (let item of s) {
        console.log(item, s)
        t = t.replace(item, '')
      }
      return t
    };
    console.log(findTheDifference('asdf', 'afads'))
  </script>
</body>

</html>